chore: Re-organize sub-modules to extract the client part from core (#149)

# Description

This PR is made for better organize the different sub-modules,
essentially the core one by extracing the specification (the model) from
the client, in a similar way as what as been done for the server part.

The goal for this split is to make it easier to provide other client
implementation in a near future.

Although code as been spread across new modules, it does not impact the
way it is used as the same packages as been kept. Therefore, it does not
impact much the main readme

- [X ] Follow the [`CONTRIBUTING` Guide](../CONTRIBUTING.md).
- [ X] Make your Pull Request title in the
<https://www.conventionalcommits.org/> specification.
- Important Prefixes for
[release-please](https://github.com/googleapis/release-please):
- `fix:` which represents bug fixes, and correlates to a
[SemVer](https://semver.org/) patch.
- `feat:` represents a new feature, and correlates to a SemVer minor.
- `feat!:`, or `fix!:`, `refactor!:`, etc., which represent a breaking
change (indicated by the `!`) and will result in a SemVer major.
- [ X] Ensure the tests pass
- [ X] Appropriate READMEs were updated (if necessary)

Fixes #<issue_number_goes_here> 🦕

---------

Co-authored-by: Kabir Khan <[email protected]>

Author: brasseld

README.md

@@ -34,15 +34,20 @@ The A2A Java SDK provides a Java server implementation of the [Agent2Agent (A2A)
 - [Add a class that creates an A2A Agent Executor](#3-add-a-class-that-creates-an-a2a-agent-executor)
 - [Add an A2A Java SDK Server Maven dependency to your project](#4-add-an-a2a-java-sdk-server-maven-dependency-to-your-project)
 
-### 1. Add the A2A Java SDK Core Maven dependency to your project
+### 1. Add the A2A Java SDK Maven dependencies to your project
 
 > **Note**: The A2A Java SDK isn't available yet in Maven Central but will be soon. For now, be
 > sure to check out the latest tag (you can see the tags [here](https://github.com/a2aproject/a2a-java/tags)), build from the tag, and reference that version below. For example, if the latest tag is `0.2.3`, you can use the following dependency.
 
 ```xml
 <dependency>
     <groupId>io.a2a.sdk</groupId>
-    <artifactId>a2a-java-sdk-core</artifactId>
+    <artifactId>a2a-java-sdk-client</artifactId>
+    <version>0.2.3</version>
+</dependency>
+<dependency>
+    <groupId>io.a2a.sdk</groupId>
+    <artifactId>a2a-java-sdk-server-common</artifactId>
     <version>0.2.3</version>
 </dependency>
 ```

client/pom.xml

@@ -0,0 +1,45 @@
+<?xml version="1.0"?>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"
+         xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>io.a2a.sdk</groupId>
+        <artifactId>a2a-java-sdk-parent</artifactId>
+        <version>0.2.4-SNAPSHOT</version>
+    </parent>
+    <artifactId>a2a-java-sdk-client</artifactId>
+
+    <packaging>jar</packaging>
+
+    <name>Java SDK A2A Client</name>
+    <description>Java SDK for the Agent2Agent Protocol (A2A) - Client</description>
+
+    <dependencies>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>a2a-java-sdk-common</artifactId>
+            <version>${project.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>a2a-java-sdk-spec</artifactId>
+            <version>${project.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.mock-server</groupId>
+            <artifactId>mockserver-netty</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+</project>

core/src/main/java/io/a2a/spec/A2A.java client/src/main/java/io/a2a/A2A.javacore/src/main/java/io/a2a/spec/A2A.java renamed to client/src/main/java/io/a2a/A2A.java

@@ -1,29 +1,23 @@
-package io.a2a.spec;
+package io.a2a;
 
 import java.util.Collections;
 import java.util.Map;
 
 import io.a2a.client.A2ACardResolver;
 import io.a2a.http.A2AHttpClient;
 import io.a2a.http.JdkA2AHttpClient;
+import io.a2a.spec.A2AClientError;
+import io.a2a.spec.A2AClientJSONError;
+import io.a2a.spec.AgentCard;
+import io.a2a.spec.Message;
+import io.a2a.spec.TextPart;
 
 
 /**
  * Constants and utility methods related to the A2A protocol.
  */
 public class A2A {
 
-    public static final String CANCEL_TASK_METHOD = "tasks/cancel";
-    public static final String GET_TASK_PUSH_NOTIFICATION_CONFIG_METHOD = "tasks/pushNotificationConfig/get";
-    public static final String GET_TASK_METHOD = "tasks/get";
-    public static final String SET_TASK_PUSH_NOTIFICATION_CONFIG_METHOD = "tasks/pushNotificationConfig/set";
-    public static final String SEND_TASK_RESUBSCRIPTION_METHOD = "tasks/resubscribe";
-    public static final String SEND_STREAMING_MESSAGE_METHOD = "message/stream";
-    public static final String SEND_MESSAGE_METHOD = "message/send";
-
-    public static final String JSONRPC_VERSION = "2.0";
-
-
     /**
      * Convert the given text to a user message.
      *
@@ -133,16 +127,4 @@ public static AgentCard getAgentCard(A2AHttpClient httpClient, String agentUrl,
         A2ACardResolver resolver = new A2ACardResolver(httpClient, agentUrl, relativeCardPath, authHeaders);
         return resolver.getAgentCard();
     }
-
-    protected static boolean isValidMethodName(String methodName) {
-        return methodName != null && (methodName.equals(CANCEL_TASK_METHOD)
-                || methodName.equals(GET_TASK_METHOD)
-                || methodName.equals(GET_TASK_PUSH_NOTIFICATION_CONFIG_METHOD)
-                || methodName.equals(SET_TASK_PUSH_NOTIFICATION_CONFIG_METHOD)
-                || methodName.equals(SEND_TASK_RESUBSCRIPTION_METHOD)
-                || methodName.equals(SEND_MESSAGE_METHOD)
-                || methodName.equals(SEND_STREAMING_MESSAGE_METHOD));
-
-    }
-
 }

…/java/io/a2a/client/A2ACardResolver.java …/java/io/a2a/client/A2ACardResolver.javacore/src/main/java/io/a2a/client/A2ACardResolver.java renamed to client/src/main/java/io/a2a/client/A2ACardResolver.java core/src/main/java/io/a2a/client/A2ACardResolver.java renamed to client/src/main/java/io/a2a/client/A2ACardResolver.java

@@ -1,16 +1,6 @@
 package io.a2a.client;
 
-import static io.a2a.spec.A2A.CANCEL_TASK_METHOD;
-import static io.a2a.spec.A2A.GET_TASK_METHOD;
-import static io.a2a.spec.A2A.GET_TASK_PUSH_NOTIFICATION_CONFIG_METHOD;
-import static io.a2a.spec.A2A.JSONRPC_VERSION;
-import static io.a2a.spec.A2A.SEND_MESSAGE_METHOD;
-import static io.a2a.spec.A2A.SEND_STREAMING_MESSAGE_METHOD;
-import static io.a2a.spec.A2A.SEND_TASK_RESUBSCRIPTION_METHOD;
-import static io.a2a.spec.A2A.SET_TASK_PUSH_NOTIFICATION_CONFIG_METHOD;
 import static io.a2a.util.Assert.checkNotNullParam;
-import static io.a2a.util.Utils.OBJECT_MAPPER;
-import static io.a2a.util.Utils.unmarshalFrom;
 
 import java.io.IOException;
 import java.util.Map;
@@ -24,7 +14,7 @@
 import io.a2a.http.A2AHttpClient;
 import io.a2a.http.A2AHttpResponse;
 import io.a2a.http.JdkA2AHttpClient;
-import io.a2a.spec.A2A;
+import io.a2a.A2A;
 import io.a2a.spec.A2AClientError;
 import io.a2a.spec.A2AClientJSONError;
 import io.a2a.spec.A2AServerException;
@@ -36,6 +26,7 @@
 import io.a2a.spec.GetTaskRequest;
 import io.a2a.spec.GetTaskResponse;
 import io.a2a.spec.JSONRPCError;
+import io.a2a.spec.JSONRPCMessage;
 import io.a2a.spec.JSONRPCResponse;
 import io.a2a.spec.MessageSendParams;
 import io.a2a.spec.PushNotificationConfig;
@@ -49,6 +40,7 @@
 import io.a2a.spec.TaskPushNotificationConfig;
 import io.a2a.spec.TaskQueryParams;
 import io.a2a.spec.TaskResubscriptionRequest;
+import io.a2a.util.Utils;
 
 /**
  * An A2A client.
@@ -158,8 +150,8 @@ public SendMessageResponse sendMessage(MessageSendParams messageSendParams) thro
      */
     public SendMessageResponse sendMessage(String requestId, MessageSendParams messageSendParams) throws A2AServerException {
         SendMessageRequest.Builder sendMessageRequestBuilder = new SendMessageRequest.Builder()
-                .jsonrpc(JSONRPC_VERSION)
-                .method(SEND_MESSAGE_METHOD)
+                .jsonrpc(JSONRPCMessage.JSONRPC_VERSION)
+                .method(SendMessageRequest.METHOD)
                 .params(messageSendParams);
 
         if (requestId != null) {
@@ -210,8 +202,8 @@ public GetTaskResponse getTask(TaskQueryParams taskQueryParams) throws A2AServer
      */
     public GetTaskResponse getTask(String requestId, TaskQueryParams taskQueryParams) throws A2AServerException {
         GetTaskRequest.Builder getTaskRequestBuilder = new GetTaskRequest.Builder()
-                .jsonrpc(JSONRPC_VERSION)
-                .method(GET_TASK_METHOD)
+                .jsonrpc(JSONRPCMessage.JSONRPC_VERSION)
+                .method(GetTaskRequest.METHOD)
                 .params(taskQueryParams);
 
         if (requestId != null) {
@@ -260,8 +252,8 @@ public CancelTaskResponse cancelTask(TaskIdParams taskIdParams) throws A2AServer
      */
     public CancelTaskResponse cancelTask(String requestId, TaskIdParams taskIdParams) throws A2AServerException {
         CancelTaskRequest.Builder cancelTaskRequestBuilder = new CancelTaskRequest.Builder()
-                .jsonrpc(JSONRPC_VERSION)
-                .method(CANCEL_TASK_METHOD)
+                .jsonrpc(JSONRPCMessage.JSONRPC_VERSION)
+                .method(CancelTaskRequest.METHOD)
                 .params(taskIdParams);
 
         if (requestId != null) {
@@ -310,8 +302,8 @@ public GetTaskPushNotificationConfigResponse getTaskPushNotificationConfig(TaskI
      */
     public GetTaskPushNotificationConfigResponse getTaskPushNotificationConfig(String requestId, TaskIdParams taskIdParams) throws A2AServerException {
         GetTaskPushNotificationConfigRequest.Builder getTaskPushNotificationRequestBuilder = new GetTaskPushNotificationConfigRequest.Builder()
-                .jsonrpc(JSONRPC_VERSION)
-                .method(GET_TASK_PUSH_NOTIFICATION_CONFIG_METHOD)
+                .jsonrpc(JSONRPCMessage.JSONRPC_VERSION)
+                .method(GetTaskPushNotificationConfigRequest.METHOD)
                 .params(taskIdParams);
 
         if (requestId != null) {
@@ -353,8 +345,8 @@ public SetTaskPushNotificationConfigResponse setTaskPushNotificationConfig(Strin
     public SetTaskPushNotificationConfigResponse setTaskPushNotificationConfig(String requestId, String taskId,
                                                                                PushNotificationConfig pushNotificationConfig) throws A2AServerException {
         SetTaskPushNotificationConfigRequest.Builder setTaskPushNotificationRequestBuilder = new SetTaskPushNotificationConfigRequest.Builder()
-                .jsonrpc(JSONRPC_VERSION)
-                .method(SET_TASK_PUSH_NOTIFICATION_CONFIG_METHOD)
+                .jsonrpc(JSONRPCMessage.JSONRPC_VERSION)
+                .method(SetTaskPushNotificationConfigRequest.METHOD)
                 .params(new TaskPushNotificationConfig(taskId, pushNotificationConfig));
 
         if (requestId != null) {
@@ -403,8 +395,8 @@ public void sendStreamingMessage(String requestId, MessageSendParams messageSend
         checkNotNullParam("failureHandler", failureHandler);
 
         SendStreamingMessageRequest.Builder sendStreamingMessageRequestBuilder = new SendStreamingMessageRequest.Builder()
-                .jsonrpc(JSONRPC_VERSION)
-                .method(SEND_STREAMING_MESSAGE_METHOD)
+                .jsonrpc(JSONRPCMessage.JSONRPC_VERSION)
+                .method(SendStreamingMessageRequest.METHOD)
                 .params(messageSendParams);
 
         if (requestId != null) {
@@ -462,8 +454,8 @@ public void resubscribeToTask(String requestId, TaskIdParams taskIdParams, Consu
         checkNotNullParam("failureHandler", failureHandler);
 
         TaskResubscriptionRequest.Builder taskResubscriptionRequestBuilder = new TaskResubscriptionRequest.Builder()
-                .jsonrpc(JSONRPC_VERSION)
-                .method(SEND_TASK_RESUBSCRIPTION_METHOD)
+                .jsonrpc(JSONRPCMessage.JSONRPC_VERSION)
+                .method(TaskResubscriptionRequest.METHOD)
                 .params(taskIdParams);
 
         if (requestId != null) {
@@ -502,13 +494,13 @@ private A2AHttpClient.PostBuilder createPostBuilder(Object value) throws JsonPro
         return httpClient.createPost()
                 .url(agentUrl)
                 .addHeader("Content-Type", "application/json")
-                .body(OBJECT_MAPPER.writeValueAsString(value));
+                .body(Utils.OBJECT_MAPPER.writeValueAsString(value));
 
     }
 
     private <T extends JSONRPCResponse> T unmarshalResponse(String response, TypeReference<T> typeReference)
             throws A2AServerException, JsonProcessingException {
-        T value = unmarshalFrom(response, typeReference);
+        T value = Utils.unmarshalFrom(response, typeReference);
         JSONRPCError error = value.getError();
         if (error != null) {
             throw new A2AServerException(error.getMessage() + (error.getData() != null ? ": " + error.getData() : ""));